Currently there is substantial interest in simultaneously controlling the flow of exhaust gases and building air through both the flue tube and the vent pipe of fuel fired heating appliances such as gas fired water heaters. The reason for this interest is that substantial energy losses take place by the flow of building air through the appliance's flue tube and exhaust hood during periods in which the appliance burner is not firing. This air flow not only cools the interior and contents of the appliance but causes heated building air to escape to the exterior of the building.
Many different damper arrangements have been proposed to control this flow. Typically, these prior damper assemblies have required substantial redesign of the appliance's draft hood and have entailed somewhat complicated mounting arrangements. Additionally, in order to achieve the proper flow through and around these assemblies it has generally been necessary to substantially increase the size of the draft hood portion of the appliance.